Potassium and Calcium nitrates are also used in agriculture In the
former the nitrogen is estimated as in sodium nitrate am the other tests
indicated in the article on potassium nitrate (chapter on Chemical Pro-
ducts ") and the determination of the potassium may also be carried out
(see General Methods, 5)- With calcium nitrate, the determination of the
nitrogen is usually sufficient.
ic, nitric acid) now sold as a fer-
nitntfo-nitritc, with 14-5% N-
The commercial product is a greyish-black, line- or granulated, powder
and consists of a mixture of calcium eyanamide (Cat N.) with hme, carbon
and various impurities (calcium carbide, sulphur and phosphorus compounds,
its vame depends essentially on its nitrogen content, which is deter-
mined by Ulsch's modified Kjeldahl method (see General Methods, 3, Q
on C"5 -i gram of substance. The ac.tion is to lie regarded as complete after
about three hours' boiling with phospliosnlphurie acid, since the liquid
does not become clear and colourless owing to the presence of carbon in
suspension. It is also sufficient to boil i grain of the substance for ^ hours
with 30 c.c. of dilute sulphuric, acid (;i : i) and a drop of mercury.
Pure calcium eyaiuuniUe (Ca.CNL) contains jj",, N ; the commeivial product,
consisting on the average of <>o% °f (lie cyauauiide, ,;o% of lime, 10% of car-
bon and 10% of various extraneous substances, contain:; i;j •«',,',% N.
By phosphates arc understood products containing tricalcinm phos-
phate,, C'a,!|(I>O<l)a, such as Mineral />//i«/>//(//V.s (/•>/t<is/ilu>ri(t>st ti/Hililes, co-pro-
Hies) ; hones, such as hone meal and hone ash ; and hone Mtiek.
Analysis of these products includes mainly determinations of the mois-
ture and phosphoric, anhydride ; in sonic cases also the nitrogen (in bones
and the ash ol' raw bones), ferric oxide and alumina (in mineral phosphates)
and others indicated in 5 (below), when a complete analysis is required.
1. Moisture.- -See General Methods, 2.
2, Phosphoric Anhydride (total), .Sir General Methods, 4.
3. Nitrogen, See General .Methods, 3, ('.
4, Ferric Oxide and Alumina, f»7ifsr/s metlmtt, 5 grams of the
substance arc boiled for about ju minutes in a 250 c,c. measuring flusli
with 50 75 c.c. of water, ,;o c.c. of nmc. In diorhloric acitl awl 5 c.c. of cone
nitric acid, the liquid being made up tu volume <>n entiling and filteredtage of chlorate varies from o-i to i. Commer-